The Effects of Building Representation and Clustering in Large-Eddy Simulations of Flows in Urban Canopies

We perform large-eddy simulations of neutral atmospheric boundary-layer flow over a cluster of buildings surrounded by relatively flat terrain. The first investigated question is the effect of the level of building detail that can be included in the numerical model, a topic not yet addressed by any previous study. The simplest representation is found to give similar results to more refined representations for the mean flow, but not for turbulence. The wind direction on the other hand is found to be important for both mean and turbulent parameters. As many suburban areas are characterised by the clustering of buildings and homes into small areas separated by surfaces of lower roughness, we look at the adjustment of the atmospheric surface layer as it flows from the smoother terrain to the built-up area. This transition has unexpected impacts on the flow; mainly, a zone of global backscatter (energy transfer from the turbulent eddies to the mean flow) is found at the upstream edge of the built-up are

What static and dynamic properties should slalom skis possess? Judgments by advanced and expert skiers

Flexural and torsional rigidity are important properties of skis. However, the flexural and torsional rigidity that lead to optimal performance remain to be established. In the present study, four pairs of slalom skis that differed in flexural and torsional rigidity were tested by advanced and expert skiers. Using a 10-item questionnaire, different aspects of the skis’ performance were rated on a 9-point scale. For each pair of skis, physical measurements were compared with the ratings of the two groups of skiers. Correlations (Spearman) were then determined between (i) different mechanical properties of the skis (static and dynamic), (ii) subjective assessments of the participants, and (iii) properties of the skis and the participants’ assessments. The latter showed that expert skiers rate the aspects of the skis more accurately than advanced skiers. Importantly, expert skiers are particularly sensitive to torsion of the skis. These results suggest that such highly rated elements should be addressed in future ski designs

An international comparison of phase angle standards between the novel impedance bridges of CMI, INRIM and METAS

We report here the results of a comparison of electrical impedance standards aimed at evaluating four novel digital impedance bridges developed by the national metrology institutes CMI, INRIM and METAS. This comparison, which is the first of its kind, involved phase angle impedance standards developed by TÜBITAK UME with phase angles of  ± 30° and  ± 60°, and magnitudes ranging from about 100 Ω to 1 MΩ. The comparison demonstrated agreement among the measurement results obtained with the different bridges, and allowed us to gather information on the stability of the phase standards and on more critical aspects related to the characterization of the bridges

An international trilateral comparison among the newest generations of digital and Josephson impedance bridges

This work reports and thoroughly discusses the results of an onsite trilateral comparison between a dual Joseph-son impedance bridge developed by METAS and the electronic fully-digital impedance bridges developed by CMI and INRIM-POLITO. The target accuracies of the bridges are at the level of 10−9–10−8 for the former and at the level of parts in 107 for the latter. The bridges were tested with R : R and R : C standards, with nominal magnitudes of 12.9kΩ, and with a quantum Hall resistance standard, in conditions suitable for the primary direct realization of the impedance units ohm and farad from AC quantum Hall resistance standards or from AC/DC calculable transfer resistance standards calibrated against DC quantum Hall resistance standards. The results were fully compatible at the expected level of uncertainty for what concerns the magnitude ratio, but phase measurements with R : C standards showed some incompatibilities

Lagrangian Stochastic Modeling of Heavy Particle Trajectories in Atmospheric Turbulence

Particle transport in atmospheric boundary layer turbulence is simulated using Lagrangian Stochastic Models (LSM) coupled with a Large Eddy Simulation (LES) model of atmospheric boundary layer flow. The aim of this work is to improve the accuracy of transport modeling of various natural tracers such as snow flakes and pollen and anthropogenic tracers such as reactive and non reactive pollutants. Lagrangian Stochastic Models are based on the assumption that the pair of variables describing position and velocity of a particle (x,u) evolve as a Markovian process. The particle’s trajectories in six-dimensional phase space can be modeled based on concepts similar to those in the modeling of Brownian motion. In this work, the LSM technique, modified by Weil et al. 2004 to be compatible with LES, is extended to heavy particles. In this technique, the particle follows the resolved turbulent motions simulated by the LES, while the motions due to the unresolved scales are included as a stochastic contribution. The effect of the particle’s mass is accounted for by imposing a settling velocity and reducing the Lagrangian autocorrelation time-scale. The model results are validated against experimental data from field measurements of the dispersion of glass beads in the atmospheric boundary layer

A computational framework for the design of optimal protein synthesis

Despite the establishment of design principles to optimize codon choice for heterologous expression vector design, the relationship between codon sequence and final protein yield remains poorly understood. In this work, we present a computational framework for the identification of a set of mutant codon sequences for optimized heterologous protein production, which uses a codon-sequence mechanistic model of protein synthesis. Through a sensitivity analysis on the optimal steady state configuration of protein synthesis we are able to identify the set of codons, that are the most rate limiting with respect to steady state protein synthesis rate, and we replace them with synonymous codons recognized by charged tRNAs more efficient for translation, so that the resulting codon-elongation rate is higher. Repeating this procedure, we iteratively optimize the codon sequence for higher protein synthesis rate taking into account multiple constraints of various types. We determine a small set of optimized synonymous codon sequences that are very close to each other in sequence space, but they have an impact on properties such as ribosomal utilization or secondary structure. This limited number of sequences can then be offered for further experimental study. Overall, the proposed method is very valuable in understanding the effects of the different properties of mRNA sequences on the final protein yield in heterologous protein production and it can find applications in synthetic biology and biotechnology

Trilateral Comparison Among Digital and Josephson Impedance Bridges

In this work, we present the results of an onsite trilateral comparison between a dual Josephson impedance bridge developed by METAS and the electronic fully-digital impedance bridges developed by CMI and INRIM-POLITO. The target accuracies of the bridges are at the 10 −8 level for the former and at the 10 −7 for the latter. Here we report the results of the calibration of a 10nF capacitance standard against a 12.9kΩ calculable resistance standard at 1233Hz, conditions suitable for the primary direct realization of the impedance units ohm and farad from AC quantum Hall resistance standards or from AC/DC calculable transfer resistance standards calibrated against DC quantum Hall resistance standards